In some fluid systems today, torque developed by a fluid motor is controlled strictly by a control valve. In these systems, the control valves are pilot operated and have feedback passages sensing the pressure in the fluid lines between the motor and the control valve. The feedback passages are communicated to small pistons in the control valve for counteracting the force of the pilot fluid to move the spool in the control valve to a position for passing only the fluid required to maintain a desired output torque by the fluid motor. The remainder of the fluid is returned to tank at high pressure over a relief valve or through an exhaust port in the control valve.
Other systems use a pump control that provides a control over the displacement of the flow from the pump in response to the load signal or system requirements reaching a predetermined pressure level.
One of the problems encountered with such systems is the need to have an elaborate control valve with several extra components. Some of these systems also do not allow the operator to control the amount of torque applied by the motor during acceleration or deceleration.
The present invention is directed to overcoming one or more of the problems as set forth above.